Infrared wavelength selective thermal emission based on Tamm plasmon polaritons (TPPs) is experimentally demonstrated. Unlike conventional TPP structures having a thin metal layer on a DBR, the proposed structure has a thick metal under a DBR which is more robust for thermal radiation. The number of DBR pairs is a critical factor to maximize the narrowband emission: It has to satisfy the impedance matching condition, which varies with the choice of metal film. The proposed structure can achieve twice higher Q-factor for the measured emissivity compared to typical plasmonic thermal emitters. The structure is one dimensional, only consists of multilayers, and free from nano-patterning, offering a practical design in applications such as gas sensing, narrowband IR sources and in thermophotovoltaics. TOC

High-refractive-index (HRI) nanostructures support optically induced electric dipole (ED) and magnetic dipole (MD) modes that can be used to control scattering and achieve narrowband absorption. In this work, a high-absorptance device is proposed and realized by using amorphous silicon nanoantenna (a-Si NA) arrays that suppress backward and forward scattering with engineered structures and in particular periods. The overlap of ED and MD resonances, by designing an array with a specific period and exciting lattice resonances, is experimentally demonstrated. The absorptance of a-Si NA arrays increases 3-fold in the near-infrared range in comparison to unpatterned silicon films. Nonradiating a-Si NA arrays can achieve high absorptance with a small resonance bandwidth (Q = 11.89) at a wavelength of 785 nm. The effect is observed not only due to the intrinsic loss of material but by overlapping the ED and MD resonances.

Selective thermal emissions from the excitation of Tamm plasmon polaritons (TPPs) are demonstrated. A TPP structure is composed of a distributed Bragg reflector (DBR) and a thin metal film on top. The tunability of the thermal emission was experimentally achieved only by changing the DBR's photonic bandgap. Low cost and large area selective thermal emitters can be realized by TPP-based structures.

generation, [4][5][6] radiative cooling, [7] and thermophotovoltaics (TPVs). [8] When selective thermal emitters are intended to emit in shorter mid IR range (e.g., an emitter for TPV system), the emitter has to be heated above one thousand kelvin. [9] Refractory metals such as molybdenum (Mo) [10] and tungsten (W) [11] are required in such cases. However, searching for alternative plasmonic materials is essential for reducing the material cost as well as for material research interest.Transition metal nitrides such as titanium nitride (TiN) and zirconium nitride (ZrN) also possess melting point as high as ≈3000 °C, [12][13][14] hence regarded as good candidate materials for thermal emitters. In addition, transition metal nitrides are regarded as alternative plasmonic materials in the visible to infrared region due to their high carrier concentrations up to 10 21 -10 22 cm −3 . [15] Among transition metal nitrides, TiN receives many attentions as an alternative plasmonic material in the past decades. [16][17][18] One of the advantages of using TiN is that it can be used in much higher temperature than other plasmonic materials. [19][20][21] However, there are only limited studies on thermal emitters using TiN so far.To demonstrate wavelength selective thermal emission, nanostructures have been investigated intensively [22,23] rather than microcavity structures which have been studied in 1990's and early 2000's. [24][25][26] Variety of nanostructures have been proposed, such as 1D grating, [27,28] 2D or 3D metallic photonic crystals, [2,29,30] and metal-insulator-metal (MIM) metamaterial structures. [31] Among those nanostructures, MIM metamaterial structures are easy to achieve wavelength selective emissions with single or multibands whose bandwidths and emission wavelengths are adjustable. [32] However, the requirement of nanofabrication, such as e-beam lithography, leads to limitations in large area fabrications.In contrast, thin-film based devices are the candidates for large area samples which do not require nanopatterning. [33,34] One way to optimize 1D thin film structures is via manipulating the phase-shifting layers in Gires-Tournois resonator. [35] Several different multilayer thin-film designs have been explored, which include Fabry-Perot cavity with either distributed Bragg reflectors (DBRs) and/or metallic mirror(s) and Tamm plasmon polaritons (TPPs) structures. For MIM structures (i.e., Fabry-Perot cavity), standing waves exist within the dielectric layer to form a cavity resonator. [36][37][38] In contrast, 1D TPP structure can excite TPP resonance at the interface of a A refractory wavelength selective thermal emitter is experimentally realized by the excitation of Tamm plasmon polaritons (TPPs) between a titanium nitride (TiN) thin film and a distributed Bragg reflector (DBR). The absorptance reaches nearly unity at ≈3.73 μm with the bandwidth of 0.36 μm in the experiment. High temperature stabilities are confirmed up to 500 and 1000 °C in ambient and in vacuum, respectively. When the TiN TPP stru...

High-power impulse magnetron sputtering (HiPIMS) was used to deposit titanium nitride (TiN) thin films with high electron density as alternative plasmonic materials. TiN thin films with thicknesses of 20-40 nm were deposited with different average sputtering powers, and exhibited metallic-and dielectric-like optical properties. When the sputtering power was increased from 80 W to 300 W, denser polycrystalline TiN thin films were obtained at room temperature (RT) with a conductivity 25 times that of the low-sputtering-power film. With sufficient average power (≥ 180 W), the films exhibited metallic-like optical properties, and a conductivity of >10 5 S/m. By using HiPIMS deposition, good-quality metallic-like TiN thin films could be fabricated at RT without heating the substrate.